Title : Recent development of Ni based composite as electrocatalysts for proton exchange membrane fuel cells
he increasing worldwide energetic demands in the last decade’s push humankind to seek for alternatives to the actual environmental unfriendly carbon-based energy production processes. In this regard, alkaline water electrolysis, fuel cells and metal-air batteries are nowadays among the most studied energy conversion and storage systems. Proton exchange membrane fuel cells (PEMFCs) are electrochemical devices that convert chemical energy directly into electrical energy and represent the leading candidate in the alternative energy industry. PEMFC is a two electrode system, with hydrogen evolution reaction (HER) or oxygen reduction reaction (ORR) taking place at cathode, while the anode performing oxygen evolution reaction (OER) or oxidation of chemical fuels. To increase the redox reactions rate that occur at the anode and cathode of a PEMFC, a catalyst represents a prerequisite. Currently, the most active electrocatalyst is based on Pt deposited on carbon. Nevertheless, the high cost of Pt on one side and carbon corrosion, which inherently leads to loss of catalyst, on the other side, constrain the scientific community to find alternatives. Therefore, a lot of research has been devoted for the development of new electrocatalysts with low noble metal content or even for non-noble metal systems supported on oxides. During this presentation two case studies will be discussed: one presenting the improvement of the ORR activity by using Ni, Co, doped ZrO2 self-assembled electrocatalysts and the second one describing the remarkable results obtain in OER using NiSn composite. Both materials were prepared by cost efficient and facile hydrothermal template methods. The effect of the Ni, Co incorporation into ZrO2 lattice and SnO2 , respectively, on the structural, textural, surface chemistry and their activity on ORR and OER will be emphasized. The synergetic effect induced by the incorporation of Ni and Co to stabilize zirconia as well as the presence on the surface of a large percentage of hydrous species significantly enhanced the electrocatalytic activity towards ORR, while the best material used in OER that exhibit a very good catalytic activity (more than 24 mA cm-2 at an overpotential value of approx. +0.33 V vs. RHE at extremely low quantities (approx. 3.78 ng Ni species) is 5NiSn200.